Here are some useful things to know for managing an Exim server. This assumes a prior working knowledge of SMTP, MTAs, and a UNIX shell prompt.
Message-IDs and spool files
The message-IDs that Exim uses to refer to messages in its queue are mixed-case alpha-numeric, and take the form of: XXXXXX-YYYYYY-ZZ. Most commands related to managing the queue and logging use these message-ids.